Publishers and other content providers often make changes in the content of a book after publishing the first copy, especially in digital books where the distribution costs are extremely low. These changes can be versioned and can include changes such as correction of a typographical error or an optical character recognition (OCR) error, errors in translation or conversion of printed material, removal of extra white spaces, formatting changes, insertion or deletion of paragraphs, words, images, chapters, or any combination thereof. eReader software allows users to annotate such digital books by inserting comments, highlights, notes, reminders, links and so forth. However, a customer who has an old version of a digital book is unable to upgrade to a newer version of the content without losing the annotations they have made on this content, because the annotations are tied to that particular version of content and are not portable.
Thus, when a content provider makes new content available, customers are forced to choose between receiving the updated content and losing all of their custom annotations or manually reentering their custom annotations, or retaining the old content and preserving their annotations. Some marketplace statistics show that among all the customers who are offered an upgrade with the condition that they lose all their existing annotations, only about 20% of customers choose to upgrade. This means that the customer can not judge how much the new content has been improved without losing their annotations, and has a difficult time making this decision.